The last Catholic Bishop of Naumburg-Zeitz, born at Eythra, near Leipzig, 1499; died at Zeits, 3 Sept., 1564. He was the son of Cæsar von Pflug, who acted as commissary for the Elector of Saxony in the religious disputation at Leipzig in 1519. Julius entered college at Leipzig, when only eleven years of age, continued his studies at Padua, and finished them in 1521 at Bologna, obtaining the degree of Doctor of Laws. At Leipzig he was the pupil of Peter Mosellanus, and at Padua of Lazaro Buonamico. He had received benefices at Mains and Merseburg, and on his return was made dean of the cathedral of Meissen and provost at the collegiate church of Zeitz; The times in which he lived were full of troubles; Luther and his adherents were using every energy in spreading their religious views, and were supported in their work by the civil power. Pflug himself had received an education in accordance with the humanistic ideals then prevalent, while his theological knowledge, mostly self-acquired, was not very profound. He was gifted with rare diplomatic talents, and, being naturally inclined to peace and harmony, he was willing to make sacrifices even in matters of doctrine and discipline. Hence his presence was requested for nearly every theological conference held for the purpose of finding some lines of conformity in doctrine between the Catholics and Evangelicals. Thus we find him engaged at Leipzig in 1534, together with Behus and Türk against Melanchthon and Brück. In 1539 he was similarly employed by the Bishop of Meissen when the Elector of Saxony was introducing Protestantism into this diocese. It seems that, by order of the bishop, Pflug and Wicel composed a treatise giving four articles of belief, "which every Christian is bound to accept". This produced no pacifying effect, nor did the personal interview between the elector and Pflug, but rather brought about Pflug's loss of favour with John Frederick of Saxony.

On 6 January, 1541, Philip, Bishop of Naumburg, died at Freising, and ten days later the chapter received the news. Dreading the interference of the elector, the chapter ordered the occupation of the palace at Zeits which held the treasures of the diocese, and on the twentieth of the same month proceeded to the election of a successor, at which Pflug was the unanimous choice. The apprehensions of the chapter were entirely justified, for John Frederick had determined to fill any vacancy and give no chance for an election. Pflug was at the time with Cardinal Albrecht of Mains whose position brought him into close contact with the emperor. Pflug was informed of his election, and was earnestly requested not to refuse acceptance. At the imperial court he was considered the proper person to defend the independence of the diocese even against the elector. John Frederick received notice of the death of Philip on 23 January, and on the next day news of the election. He would not permit Pflug to take possession, and immediately issued orders to the city council that, until further orders, no allegiance be offered the new bishop. In the following year, on 20 January, he ordered Luther to ordain Nicholas von Amsdorf as Bishop of Naumburg. In the meantime Pflug was employed to further the reformatory projects of the emperor, and appeared in April, 1541, at the religious colloquy at Ratisbon. The book published at this meeting and the imperial edict of 29 June, 1541, called the Interim of Ratisbon, gave little satisfaction to either party: Luther and the elector wanted larger concessions, while the Catholics claimed that too much had been granted. Pflug and Gropper tried to justify themselves in a pamphlet. After the victory of Mühldorf, 24 April, 1547, over the combined forces of the Smalkaldic League, Pflug was able to enter his diocese, which had become almost entirely Protestant. He did his best to bring back the people to the Catholic faith, but in vain. He was permitted to hold Catholic service only in the cathedral of Naumburg and in the collegiate church at Zeits; the monasteries and their property remained secularized. He removed the Evangelical preachers from some of the churches, but the civil authorities restored them to their positions.

In 1549 he called the pastors to Zeits to find out their qualifications. He found a sad condition of affairs: all the priests were married with one exception, and willing rather to lose their pastorates than to give up their wives. He applied to other bishops to obtain unmarried priests, but they were unable to assist him, and thus he reported to Pope Julius III. Under this pressure he had a petition drawn up to the Cardinals Mendoza and Pole asking the toleration of married priests, though personally he preferred the unmarried clergy. Similarly he had on a former occasion expressed his opinion that many wavering minds might be kept in communion with the Church if the Holy Eucharist were administered to the laity under both species. His plan to establish a Catholic educational institution for aspirants to the clerical state failed, but he assisted students at Catholic colleges out of his own scanty income. He no longer expected any good results from disputations with the Protestants, though he was present in December, 1547, at Jüterbogk and in August, 1548, at Pegau, and assisted in framing the Interim of Augsburg. In November, 1551, he made his appearance at the Council of Trent, but on account of ill-health remained only a short time. In 1553 the elector introduced a Protestant consistory into Zeitz, and gave the cathedral of Naumburg to the common use of Catholics and Protestants. In 1559 Pflug expressed a desire for a coadjutor with the right of succession, and in 1561 he wished to resign in favour of Peter von Naumark, dean of the cathedral, but received no answer. For the temporal welfare of his diocese he made many useful regulations, lightened the burdens of the people after the ravages of the war, ordered the highways and forests to be cleared of the prowling bands of robbers, and regulated the wages and time of labour. Though Pflug has been accused of crypto-Lutheranism, no charges have ever been made against his priestly character. After death he was buried in his church at Zeits. He wrote many treatises in Latin and German on theological and kindred subjects. Their titles may be found in Ersch und Gruber, 3 Sect., XXI, 251. In the same work there is a biography from a Catholic standpoint, and another from a Protestant view. Some 115 letters of his are in the "Epistotolæ Petri Mosellani . . . ad Julium Pflugium" (ed. Müller, Leipzig, 1802).